Topological Defects 18.354 L24 Order Parameters, Broken Symmetry, and Topology James P. Sethna Laboratory of Applied Physics, Technical University of Denmark, DK-2800 Lyngby, DENMARK, and NORDITA, DK-2100 Copenhagen Ø, DENMARK and Laboratory of Atomic and Solid State Physics (LASSP), Clark Hall, Cornell University, Ithaca, NY 14853-2501, USA (Dated: May 27, 2003, 10:27 pm) dunkel@mit.edu
• work hardening, etc • optical effects order-parameter fields are discontinuities in Topological defects "umbilic defects" in a nematic liquid crystal
order = symmetry = invariance � (under certain group actions ) symmetry groups can be discrete, continous, Lie-groups, ….
More or less symmetric ?
More or less symmetric ? Mg 2 Al 4 Si 5 O 18 http://www.doitpoms.ac.uk/tlplib/crystallography3/printall.php
More or less symmetric ? broken continuous translation/rotation symmetry (invariance)
Order parameters: 2D crystal 4 � dx ( κ / 2)( du/dx ) 2 . E = u + a ˆ x = ⃗ u + ma ˆ x + na ˆ ⃗ u ≡ ⃗ y.
Order parameters: magnets tant.
Order parameters: nematic liquid crystals “projective plane” = half-sphere with opposite points on equator identified
Topological defects
Work hardening
Disclinations edge screw
Disclineations
Bacterial vortices PIV +1 -1 -1 +1 Dunkel et al PRL 2013
Active nematics Dogic lab (Brandeis) Nature 2012
Active nematics Giomi et al PRL 2012
Defects in nematics winding number
Defects in nematics winding number
Two-Dimensional Nematic Colloidal Crystals Self-Assembled by Topological Defects Igor Musevic et al. Science 313 , 954 (2006); DOI: 10.1126/science.1129660 s bilized ). taneously geometric l- col- p fabrication loids re- l- ecision micro- a- ce d s. ic id
Two-Dimensional Nematic Colloidal Crystals Self-Assembled by Topological Defects Igor Musevic et al. Science 313 , 954 (2006); DOI: 10.1126/science.1129660
Reconfigurable Knots and Links in Chiral Nematic Colloids Uros Tkalec et al. Science 333 , 62 (2011); DOI: 10.1126/science.1205705 efect ts s. g nt rs a he on e ori- o- Defect dimer, re nknot. e topologi- o loops. d- ns numerical- u-de el l- nd r- the fu- are by using a program for representing knots ( 33 ) to show the relaxation
Recommend
More recommend